Conventionally, in a known image forming apparatus such as a laser printer, a developer cartridge including a developing roller for supplying a toner to a photosensitive drum is detachably attachable to an image forming apparatus body which includes a photosensitive drum to be formed with an electrostatic latent image.
To prevent the developer cartridge from dropping off from the image forming apparatus body or to position the developer cartridge with respect to the photosensitive drum, a various types of units have been proposed to fix (lock) the developer cartridge at a determined position on the side of the image forming apparatus body.
For example, some developing unit is proposed to which a grip having a hook is pivotably provided. When this developing unit is disposed in a space of the electrophotographic copier body and the grip is pivoted, the hook engages with a pin in the space and the developing unit is fixed in the space.
Some copier is proposed to which a developing unit is provided with a grip member in a standable and foldable manner is detachably attachable. The arm of this grip member is integrally provided with a hook. This hook and a lock pin provided on the main body frame of the copier body configure an engaging unit which locks or unlocks the developing unit with respect to the copier.
Some electronic copier is proposed to which a developing unit provided with a handle which inclines and pivots is detachably attachable. When the protective cover of the electronic copier is opened and the developing unit is inserted in the accommodation space in the electronic copier, the hook portion integrally molded with a rotation shaft end on the handle is positioned corresponding to a support pin protruding in the accommodation space. When the developing unit is positioned in a completely attached state in the accommodation space, the handle is allowed to incline and pivot and the hook is engaged with the support pin to maintain the locking state, it becomes impossible to release the hook portion and it becomes possible to close the protective cover. On the other hand, when the developing unit is not in a regular attached state, the hook portion strikes the support pin and the handle cannot incline and pivot, and the hook portion and the support pin are in an unlocked state to stand the handle, thereby the protective cover cannot be closed.
Some developing unit detachably attachable to an image forming apparatus is proposed. The developing unit includes a grip for transportation, a second engaging portion provided on the grip and formed with a hook which engages with a first engaging portion on the side of the image forming apparatus and locks the developing unit so that it cannot be drawn out, and a coil spring which urges a second engaging portion so that the first engaging portion and the hook are engaged with each other. The drawing of the developing unit out from the image forming apparatus requires to hold the grip, move and retreat the second engaging portion from the engaged state of the first engaging portion with the hook against the urging force of the coil spring, in a direction which allows the developing unit to be drawn out from the image forming apparatus.
Some printer is proposed in which a processing unit including a photosensitive drum, a charger, a developing unit and the like as a unit is fixed by a lock unit and attached to the printer. The processing unit is provided with a grip to take out the unit and in the vicinity of the grip, and is provided with a lock releasing lever pivoting in a direction for releasing the lock unit and an urging unit for urging the lock releasing lever in a direction opposite to the direction for releasing the lock unit. When detaching the processing unit, the grip and the lock releasing lever are held together to pivot the lock releasing lever in the direction for releasing the lock unit, thereby releasing the lock unit.
In a known image forming apparatus, a developing roller is brought to press against a photosensitive drum at the printing operation in order to secure a reliable toner supply from the developing roller to the photosensitive drum.
In the lock unit described above, the developer cartridge can be reliably locked at a fixed position on the side of the image forming apparatus body. However, the developer cartridge locked to the fixed position is not allowed to move. Accordingly, the developing roller may fail to secure pressing operation with respect to the photosensitive drum, or a complicated mechanism is required in order to secure the pressing operation.